Semi-automatic welding operations where filler wire is utilized in connection with welding adjacent faces of materials such as pipelines is known. In U.S. Pat. No. 4,151,395, the problem of welding joints by filling grooves defining a weld path between work pieces is described. Large pipe sections are thus joined together in the end-to-end relationship. Thus, it is common practice to move a welding heat source such as an arc welding torch or like instrument along a predetermined weld path relative to the work while fusing and depositing filler metal in the gap from a consumable electrode source.
A welding machine is disclosed in said patent which travels on a guideband secured near the end of a pipe section which is to be welded to an adjacent pipe section. As such welding machine travels along the length of the groove to be filled, the arc is oscillated laterally, weaving back and forth across the groove. It is to be controlled in center position as well as oscillation width.
Various proposals have been made for tracking a groove between adjacent parts with external sensors of optical, mechanical or magnetic types suggested.
In U.S. Pat. No. 4,151,395, the signals employed are conditioned where characteristics of the arc itself are sensed for providing the necessary signal input.
In U.S. Pat. No. 4,158,124, a system is disclosed wherein the weld current is integrated as it approaches a groove sidewall. The integral is then compared with a reference voltage so that when the arc reaches a position within a predetermined proximity of the sidewall, the lateral travel will be arrested and thereafter reversed to travel under similar control toward the opposite sidewall. The maintenance of center line position and width are both accomplished in the same operation.